IntroductionLipids are very diverse in both their respective structures and functions. These diverse compounds that make up the lipid family are so grouped because they are insoluble in water. They are however soluble in other organic solvents such as ether, acetone and other lipids. Major lipid groups include fats, phospholipids, steroids and waxes.This definition has echoes of Bloors "simple and compound lipoids". In practice, it is often necessary to subdivide the main groups further. For example, the complex lipids for many purposes are best considered in terms of either the glycerophospholipids (or simply as phospholipids), which contain a polar phosphorus moiety and a glycerol backbone, or the glycolipids, which contain a polar carbohydrate moiety.For many years, lipids were considered to be intractable and uninteresting oily materials with twomain functions to serve as a source of energy and as the building blocks of membranes.They were certainly not considered to be appropriate candidates for such important molecular tasks as intracellular signaling or local hormonal regulation. In 1929, George and Mildred Burr demonstrated that linoleic acid was an essential dietary constituent, but it was many years before the importance of this finding was recognized by biochemists in general. With the discovery by Bergstrm, Samuelsson and others in 1964that the essential fatty acid arachidonate was the biosynthetic precursor of the prostaglandins with their effects on inflammation and other disease states, the scientific world in general began to realize that lipids were much more interesting than they had previously thought.A major milestone was achieved in 1979 with the discovery of the first biologically active phospholipid, platelet-activating factor. At about the same time, there arose an awareness of the distinctive functions of phosphatidylinositol and its metabolites. Since then, virtually every individual lipid class has been found to have some unique biological role that is distinct from its function as a source of energy or as a simple construction unit of a membrane. Indeed it is now recognized that lipids in membranes function also in the trafficking of cellular constituents, the regulation of the activities of membrane proteins and signaling. All multi-cellular organisms, use chemical messengers to send information between organelles and to other cells and as relatively small hydrophobic molecules, lipids are excellent candidates for signaling purposes.The fatty acid constituents have well-defined structural features, such as cis-double bonds in particular positions, which can carry information by binding selectively to specific receptors. In esterified form, they can infiltrate membranes or be translocated across them to carry signals to other cells. During transport, they are usually bound to proteins so their effective solution concentrations are very low, and they are can be considered to be inactive until they reach the site of action and encounter the appropriate receptor. Storage lipids, such as triacylglycerols, in their cellular context are inert, and indeed esterification with fatty acids may be a method of de-activating steroidal hormones, for example, until they are actually required. In contrast, polar phospholipids have both hydrophobic and hydrophilic sites that can bind via various mechanisms to membrane proteins and influence their activities. Glycosphingolipids carry complex carbohydrate moieties that have a part to play in the immune system, for example. Lipids have been implicated in a number of human disease states, including cancer and cardiovascular disease, sometimes in a detrimental and sometimes in a beneficial manner. In short, every scientist should now be aware that lipids are just as fascinating as all the other groups of organic compound that make up living systems.

ResultsA. Acrolein TestSampleResults/Descriptions

1. Glycerolblack pptodor of burnt grease

2. Coconut oilBrown pptodor of burnt grease

3. LecithinBrown pptodor of burnt grease

4. Oleic acidBlack pptodor of burnt grease

B. Test for UnsaturationSampleResults/Descriptions

1. Glycerol52 drops

2. Coconut oil80 drops

3. Lecithin15 drops

4. Oleic acid12 drops

C. Test for PhosphateSampleResults/Descriptions

LecithinFormed yellow ppt

D. Emulsification TestMixturesDescriptionSketch

1 mL coconut oil + 5 drops 0.1% bile salt solutionWhite cloudy sol

1 mL coconut oil + 5 drops H2O tiny crystal of cholesterolWhite cloudy sol

1 mL olive oil + 5 drops 1% aqueous solution of lecithinWhite cloudy sol

E. Lieberman-Burchard or Acetic Anhydride ReactionSamplesResults

CholesterolWhite cloudy sol to blue green sol

Bile saltsDirty white sol with red ppt

F. Modified Furter-Meyer TestSampleDescription

Alpha tocopherol Bronze red solution

DescriptionAcrolein Test is use to detect presence of fats or glycerin. When a fat is heated strongly in the presence of a dehydrating agent such as potassium bisulfate (KHSO4). The glycerol portion of the molecule is dehydrated to form the unsaturated aldehyde, acrolein (CH2=CHCHO). Acrolein has the odor peculiar to burnt cooking grease. Further heating results in polymerization of acrolein, which is indicated by the slight blackening of the reaction mixture. Both the pungent smell and the black color indicate the presence of glycerol and therefore fat and/or lecithin.Test for unsaturation is used to indicate the amount of presence of double bonds in the lipid sample. All neutral fats contain glycerides of some unsaturated fatty acids. These unsaturated fatty acids become saturated by taking up iodine. If the fat contains more unsaturated fatty acids, it will take up more iodine. Iodine solution reacts withstarch producing a purpleblack color. The color can be detected visually with concentrations of iodine. However the intensity of the color decreases with increasing temperature and with the presence of water-miscible, organic solvents such as ethanol. Also the test cannot be done at very low pHs due to the hydrolysis of the starch under these conditions. This test identifies the level of saturation and the number of bonds an oil, fat or lipid has. The more unsaturated, multi-bonded, the lipid is, the more it absorbs iodine. The less iodine it absorbs, the lipid is considered to be saturated, single bonded. The more the number of drops required to discharge the pink color, the less is the unsaturation.In test for phosphate, the presence of free phosphate in acidic solution can be detected by adding a molybdate to the solution. Equation illustrates the pertinent reaction between phosphate and ammonium molybdate solution in the presence of nitric acid. After a few minutes, the yellow ammonium molybdo-phosphate precipitates from the reaction mixture. When lipids containing phosphate groups in their structures are added to a strong acid solution such as the solution used here, the lipid hydrolyses, producing free phosphate.Emulsification test is used to detect polar and nonpolar groups in bile and lecithin.Lieberman-Burchard test is used to detect the presence of cholesterol. The cholesterol is react as a typical alcohol with a strong concentrated acids and the product are colored substances. Acetic anhydride are used as solvent and dehydrating agents, and the sulfuric acid is used as dehydrating and oxidizing agent.Modified Furter-Meyer Test is used to detect the presence of tocopherols by giving a bronze-red solution. Only alpha - tocopherol is recognized to meet human requirements.ConclusionAcrolein Test is use to detect presence of fats or glycerin. Test for unsaturation is used to indicate the amount of presence of double bonds in the lipid sample. In test for phosphate, the presence of free phosphate in acidic solution can be detected by adding a molybdate to the solution. Lieberman-Burchard test is used to detect the presence of cholesterol. Modified Furter-Meyer Test is used to detect the presence of tocopherols by giving a bronze-red solution.